Ugh, yea, for field use I might recommend looking for a used 2011 model. You can add in a SSD and replace the battery, and it's a lot cleaner than a battery pack to a firewire hub.
Or, maybe one of these would do the trick - http://www.usbfirewire.com/Parts/rr-cfbe-9901-np.html
- it strips all power from the FW800 cable, maybe the camera won't be confused as to where to get power. They've got FW800 power injector cables as well, but they are 4pin to 9pin.